Aviation plug



Jan. 26, 1932. c. E. LEONARD 1,842,834

Q AvIA'rIoN PLUG Filed Nov. 21, 1928 ATTORNEY which prevents gas leakageunder high as Patented Jan. 26, 1932 UNITED. STATES PATENT OFFICE.

CALEB E. LEONARD, OF MIAMI, FLORIDA, ASSIGNOR TO LEONARD SPARK PLUG COM-PANY, INCORPORATED, OF ST. PETERSBURG, FLORIDA, A CORPORATION OF FLORIDAAVIATION PLUG 'My invention relates to ignition plugs for internalcombustion engines, and its general object is to provide a structurewhich is exceptionally durable and efficient under the severeconditionsimposed by service in a high-pressure, or airplane cylinder, as well asunder less severe conditions.

, More particular objects are: To effectively radiate the heat from thecentral electrode; to provide an improved gas tight connection of theinsulator or insulators in the shell,

well .as ordinary pressures; and to provide a new and improved mainelectrode assembly.

in carrying out one of the principal objects above stated, namely, thecooling of the main or central electrode, I provide an outer or upperelectrode member which is tubular and provided an opening to atmosphere,together with aheat conducting and radiating element within such tubularelectrode which is in heat conductive connection with the main electrodeand which rapidly conveys therefrom to the chamber of the tubularelectrode, this heat being dissipated therefrom to atmosphere.

The stated features reduce strains upon the insulators, such as areordinarily occasioned by undue heating and expansion of the centralelectrode, and increase the durability and eiiiciency of the pluginvarious other ways.

, The present invention is similar in some respects to that disclosed inmy companion application, executed on even date herewith; but in thepresent case the general object is to adapt the plug for even moresevere service, such as in airplane engines, where the pressure andheating effects may be extreme. To withstand these stresses and provideelectrical and mechanical efficiency, long life and dependability, Iprovide a lower insulating member of highly refractory material,

such asquartz, and an upper insulator which has more mechanicalelasticity and is therefore better able to withstand mechanicalstresses, such, for example, as laminated mica.

in connection with the following detail description of the accompanyingdrawings, which shows one preferred embodiment. After considering thisexample, skilled persons will understand that many variations .trodemembers, some parts being in section.

Fig. 4 is a side elevation of the lower, or quartz, insulator.

The shell 1 may be of ordinary construction, except as hereinafterspecified. It is formed at an intermediate part of its length with asealing chamber having a cylindrical wall 2 terminating in a horizontalbottom shoulder 3. Above this chamber the shell is internally threadedas at 4:- The lower insulator 5, which is preferably of highlyrefractory material, such, for example, as quartz (or fused quartz), hasoppositely. ar ranged or tapering outer conical surfaces 6, the bases ofthe cones abutting at the line 7. A short upper portion of thisinsulator is cylindrical, as at '8. This insulator is secured and sealedin the shell by identical upper and lower gaskets 9 of compressiblematerial such as copper, arranged 1n rela tively reversed positions, andhaving inner conical surfaces cooperating with the cone surface 6, andouter cylindrical surfaces cooperating with the cylindrical wall of thesealing chamber. The gaskets are compressed to form a perfectlygas-tlght seai, by a ring nut- 10 having an external thread engaging theshell thread 4 and having its lower end formed to engage the uppergasket and so to compress both of the gaskets. This nut or screw ringhas in its upper face, sockets 11 to receive a spanner or other suitabletool to tighten it in position.

The upper or outer insulator 12, which is preferably of laminated mlca,or other material better able to resist mechanical shocks, is preferablyassembled as a unit with, the

central electrode structure, so that the updiair'i eter inserted witha.tight press fit in the lower end of a conducting sleeve 14, which mayin some cases be of highly conductive material, such as brass or copper,or may, if

desired, be of other metal. The sleeve 14 is desirably enclosed in atubular wrapping 15 of mica to reduce electrical and gas leak effects,the laminations of the main laminated body 12 being internally,diametered to fit above the sleeve. The laminations of the main bodyare compressed between a nut 16 engaging. a thread 17 on the upper endof the sleeve 14, and'a metal washer 18 in threaded engagement with thelower end of sleeve 14. Washer 18 preferably rests on a compressiblegasket 19 which, in turn, is seated on an internal transverse shoulder20 of the lower insulator. At its lower .end, the upper insulator has anextension 12, entering the cylindrical bore of the lower insulator, and

1 having its lower end engaging the upper face of washer 18. t v

The upper insulator 12'is desirably formed with a shoulder -at 21, and acompressible gasket 22 is located between this and the upper end of thelocking or screw ring 10 to form a gas-tightjlseal. Below shoulder 21the insulator 12 as a cylindrical surface 23 of the same diameter assurface 8 of the lower insulator and desirably an insulating sleeve 24of micais wrapped about these surfaces, fitting within the inner bore ofthe screw ring 10. a

A heat radiating rod or wire 30, which is preferably of small diameterand made' of a highly conductive material, such as brass,

copper or bronze, but otherwise may be ofot er material, is insertedwith a tight press fit in a hole in the upper end of the main or lowerelectrode 13, and this radiating mem.-

ber preferably extends through a'greater part of the length of thesleeve14, which is open at its upper end and acts 'as a radiatingchamber. Desirably rod 30 is of waved or sinuous formation to increaseits effective radiating length.

Desirably a shoulder is formed as at? 35,

. Fig. 1, in the upper insulator'a short distance above bushing 25, thusreducing or preventing spark-jumping from the shell or bushing to thecentral electrode structure.

The central structure, including the upper tor 12, by which shoulder 21is located down on the compressible gasket 22, the lower end of thebushing also seating against this gasket.

An suitable lower or grounded electrode may e provided. Preferably thisis in the form of a strip or block 40 bridging the lower or sparkingchamber 41 of the shell and secured positively against any loosening orfalling out by having its ends engaged in undercut sockets, or anannular channel 42 in the shell bore. The actual sparking element is araised member 43 on the upper face of the block, in properly spacedrelation to the lower end of the main electrode 13.

The central electrode structure, including the members 14, 18, 13 and30, is, as above explained, a practically unitary structure, the part-sbeing in tight heat conducting contact. In operation, therefore, heat israpid- 'ly conducted away from the lower electrode entire centralstructure, except the lower insulator 5, may be removed as a unit andreplaced, by the removal of the bushing.

In some cases the adjacent edges of gaskets 9 may approximately orclosely meet, when compressed, to increase the tightness of the gas sealat this point.

Also, the main electrode 13, sleeve 14, and disc (or nut) 18, may be.welded together, for greater mechanical strength and to increaseheat-conductivity.

v I claim 1. In a spark plug, a central struc re comprising aninsulator, a metal sleev therein open to atmosphere at its upper end,and a lower electrode tightly engaged in the lower lower electrodetightly engaged in the'lower end of the sleeve, and a radiating rod ofwaved formation and of small diameter in conductive connection with theupper end of the lower insulator and extending upwardly within thesleeve whereby heat is conducted from the electrode and dissipated toair within the sleeveand so to atmosphere.

'3. In a spark plug, a substantially unitary central electrode structurecomprising a sleeve open to atmosphere at its outward end, and anelectrode tightly inserted in one end thereof, and a radiating wiretightl inserted in the electrode and extending within the sleeve.

4. In a spark-plug, in combination with the shell and insulator,acentral electrode structure comprising a lower, solid electrode portionand an upper tubular conducting portion having close heat conductingconnec- Io tion to the lower portion and open to atmosphere at its upperend, and a radiating rod of smaller diameter than said tubular portionand located therein and having close heat conductive connection tothelower electrode portion.

5. In a spark plug, in combination with the shell and insulator, acentral electrode structure comprising a lower, solid electrode portionand an upper tubular conducting portionhaving close' heat conductingconnection to the lower portion and open to atmosphere at its upper end,and a radiating rod of smaller diameter than said tubular portion andlocated therein and having close heat conductive connection to the lowerelectrode portion, the radiating rod being in sinuous formation. I

6. In a spark plug,.in combination with the shell and insulator, acentral electrode structure comprising a lower, solid electrode portionandan upper tubular conducting portion having close heat conductingconnection to the lower portion andopen to atmosphere at its upper end,and a radiating rod of smaller diameter than said tubular portion andlocated therein and having close heat conductive connection to the lowerelectrode portion, said radiating rod extending through a large part ofthe length of said tubular portion. y

'In testimony whereof I aflix my signature.-

CALEB E. LEONARD.

